import 'package:flutter/material.dart';

/***
 * 入口函数
 * lc
 */
void main() => runApp(MyApp());// Dart中的箭头函数 ，
// 和kotlin很想跟下面写法效果一致lc
/***
 * 这里是android 的application类
 */
class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        /*这个地方就类似于Android中的style文件配置，主要就是主题的配置*/
        primaryColor: Colors.red,
        primaryColorDark: Colors.red,
        accentColor: Colors.orange,
        buttonTheme: ButtonThemeData(buttonColor: Colors.red,textTheme: ButtonTextTheme.primary)

      //原文：https://blog.csdn.net/yuzhiqiang_1993/article/details/84951960

        // This is the theme of your application.
        //
        // Try running your application with "flutter run". You'll see the
        // application has a blue toolbar. Then, without quitting the app, try
        // changing the primarySwatch below to Colors.green and then invoke
        // "hot reload" (press "r" in the console where you ran "flutter run",
        // or simply save your changes to "hot reload" in a Flutter IDE).
        // Notice that the counter didn't reset back to zero; the application
        // is not restarted.

      ),
      /*home指定了启动后显示的页面
      * 类似于我们在AndroidManifest中配置启动页面
      * */
      home: MyHomePage(title: '我的 Flutter Demo'),
    );
  }
}
/*
* StatefulWidget是一个有状态的控件，如果你的页面需要更新ui，那么该页面就要继承自StatefulWidget
* 如果只是一个纯展示的页面，只需要继承自StatelessWidget即可
* MyHomePage在上面已经被指定为启动页面
* 该页面有一个计数的逻辑，会更新ui，所以需要继承自StatefulWidget
* */

class MyHomePage extends StatefulWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  /*Dart 中的构造方法  {}里面的参数表示可选参数，跟kotlin概念差不多
  * this.title默认会把值赋给下面的title
  * */
  // This widget is the home page of your application. It is stateful, meaning
  // that it has a State object (defined below) that contains fields that affect
  // how it looks.

  // This class is the configuration for the state. It holds the values (in this
  // case the title) provided by the parent (in this case the App widget) and
  // used by the build method of the State. Fields in a Widget subclass are
  // always marked "final".


  final String title;
  /*所有继承自StatefulWidget的控件都要重写createState()这个方法
  * 可以理解为指定该页面的状态是由谁来控制的
  * 在Dart中下划线开头声明的变量和方法，其默认访问权限就是私有的
  * 类似于java中用private关键字修饰,只能在类的内部访问
  * */


  _MyHomePageState createState() => _MyHomePageState();
}
/*
*State是一个状态对象，<>里面是表示该状态是跟谁绑定的。
* 我们修改状态时就是在该类中进行编写
*
* */
class _MyHomePageState extends State<MyHomePage> {
  int _counter = 0;
/*技术器-1*/
  void _incrementCounter() {
    setState(() {
      // This call to setState tells the Flutter framework that something has
      // changed in this State, which causes it to rerun the build method below
      // so that the display can reflect the updated values. If we changed
      // _counter without calling setState(), then the build method would not be
      // called again, and so nothing would appear to happen.
      _counter++;
    });
  }
  /*这里我们自己新建一个方法，很简单，就是执行减一操作*/
  void _reduceCounter() {
    setState(() {
      _counter--;
    });
  }
  @override
  Widget build(BuildContext context) {
    // This method is rerun every time setState is called, for instance as done
    // by the _incrementCounter method above.
    //
    // The Flutter framework has been optimized to make rerunning build methods
    // fast, so that you can just rebuild anything that needs updating rather
    // than having to individually change instances of widgets.
    return Scaffold(
      appBar: AppBar(
        // Here we take the value from the MyHomePage object that was created by
        // the App.build method, and use it to set our appbar title.
        title: Text(widget.title),
      ),
      body: Center(
        // Center is a layout widget. It takes a single child and positions it
        // in the middle of the parent.
        child: Column(
          // Column is also layout widget. It takes a list of children and
          // arranges them vertically. By default, it sizes itself to fit its
          // children horizontally, and tries to be as tall as its parent.
          //
          // Invoke "debug painting" (press "p" in the console, choose the
          // "Toggle Debug Paint" action from the Flutter Inspector in Android
          // Studio, or the "Toggle Debug Paint" command in Visual Studio Code)
          // to see the wireframe for each widget.
          //
          // Column has various properties to control how it sizes itself and
          // how it positions its children. Here we use mainAxisAlignment to
          // center the children vertically; the main axis here is the vertical
          // axis because Columns are vertical (the cross axis would be
          // horizontal).

          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              '这里是我的第一个flutter 成功项目',
            ),
            Text(
              '$_counter',
              style: Theme.of(context).textTheme.display1,
            ),
          ],
        ),
      ),

        /*浮动按钮*/
        floatingActionButton: FloatingActionButton(
          /*_incrementCounter实际上就是一个上面默认的_incrementCounter()方法，*/
          onPressed: _incrementCounter,
          tooltip: '计数器加一',
          child: Icon(Icons.add),
        ),



    );
  }
}
